1. Field of the Related Art
The present invention relates to manufacture of a semiconductor device, and particularly to a method of performing alignment in the case of exposure.
2. Description of the Invention
In manufacturing processes of a semiconductor laser, each chip is separated by cleavage. The semiconductor laser forms a resonator using a cleavage plane as a Miller plane. Thus, it is important to form an optical waveguide in the direction vertical to the cleavage plane (parallel to a crystallographic axis).
On the other hand, stripe width control of an active region is very important in order to improve controllability and uniformity of characteristics of the semiconductor laser, and use of patterning by stepper exposure has effective in the control. Also, in manufacture of a DFB (Distributed Feedback) type laser, it is significant to control a shape and a period of a diffraction grating, and use of patterning by EB (Electron Beam) exposure has effective in the control.
As a result of this, when the semiconductor laser is manufactured using an aligner, the crystal direction of a semiconductor must be accurately aligned with the direction of a marker pattern for aligning in the case of exposure.
As a method of performing this, a manufacturing method of a semiconductor device and an alignment method for providing a mark for alignment in a mask for exposure and performing alignment by this mark are disclosed in Japanese Patent Unexamined Publication No. 323575 of 1993.
In the manufacturing method disclosed in Japanese Patent Unexamined Publication No. 323575 of 1993, however, no consideration is given to accuracy in position within a substrate plane of the marker pattern, with the result that the marker pattern cannot be always formed in the same position of a substrate. Because of this, in the stepper exposure or the EB exposure, it is necessary to search the position of a stepper marker or an EB marker in manual operations, and thus, it is lacking in productivity.